An inflatable cushion disposed within a supporting structure such as a dash panel, side door or other fixed portion of a car body in opposing relation to a seat in the vehicle plays an important role in protecting the occupants of a vehicle from injury due to collision against the car body. Typically, the inflatable cushion is inflated rapidly by the pressure of a reaction gas released from an inflator during a collision. This gas generation typically takes place when a gas-generating agent in the inflator induces a chemical reaction by a collision signal from a collision-detecting sensor when the deceleration of the vehicle exceeds a certain level. The gas which is generated by the generator is then conveyed to the inflatable cushion which expands outwardly as it fills with gas to create a protective barrier between the vehicle occupant and the dash panel or other portion of the vehicle body/internal surface against which the occupant might otherwise be thrown.
To elaborate, inflatable protective cushions used in passenger vehicles are a component of relatively complex passive restraint systems. The main elements of these systems are: an impact sensing system, an ignition system, a propellant material, an attachment device, a system enclosure, and an inflatable protective cushion. Upon sensing an impact, the propellant is ignited causing an explosive release of gases filing the cushion to a deployed state that can absorb the impact of the forward movement of a body and dissipate its energy by means of rapid venting of the gas. In the undeployed state, the cushion is stored in or near the steering column, the dashboard, in a door, in the back of a front seat, or in a vehicle roof rail, placing the cushion in close proximity to the person or object it is to protect.
Inflatable cushion systems, commonly referred to as air bag systems, have been used in the past to protect both the operator of the vehicle and passengers. Systems for the protection of the vehicle operator have typically been mounted in the steering column of the vehicle and have utilized cushion constructions directly deployable towards the driver. These driver-side cushions are typically of a relatively simple configuration in that they function over a fairly small well-defined area between the driver and the steering column. One such configuration is disclosed in U.S. Pat. No. 5,533,755 to Nelsen et al., the teachings of which are incorporated herein by reference.
The steering column mounted airbags, while effective in front impact collisions, cannot protect an occupant from many other types of crashes. Side impact airbags are notable for being of more complicated designs. Not only does a different type of area need to be protected, but the area varies greatly depending upon the automobile model. Furthermore, accidents may cause a vehicle to flip or roll, requiring that an occupant be protected from most vehicle surfaces in which they can come into contact with, or in some cases protect against gaps in the vehicle surface such as open windows.
To add to the difficulties in protecting an occupant in the case of a vehicle rollover, the time involved in rollover impacts is much greater than the time involved in impact collisions. In an impact collision the time in which an airbag deploys and an occupant hits the airbag is fractional, and as a necessary result, the deflation properties of the bag must be sufficient to minimize injury. However, the same deflation properties in a bag designed to protect in a rollover scenario are undesirable, as the time between vehicle collision and the occupant impacting with the air bag in a rollover are typically many times greater than in a straight collision. Thus an airbag for protecting the occupant in rollover situations has to stay inflated for a much longer time compared to traditional airbags. As a result of this requirement, typical manufacturing methods of sewing fabric panels to a desired shape are undesirable inasmuch as leakage of gas between fabric layers and the sewn seams is excessive for rollover applications. Airbags comprising weldable composite materials having a fabric layer and a thermoplastic layer tend to be useful in rollover applications, but expensive. Accordingly, it would be desirable to minimize the use of such composite materials, where permissible.
Inasmuch as certain areas within the interior of a vehicle are highly unlikely to involve interaction with occupants during a crash, an opportunity arises to reduce costs associated with airbag systems. Localizing the cushioned portions of the system to those areas within the interior expected to impact occupants in a crash can further reduce system costs. An example of such a system is disclosed in U.S. Pat. No. 6,237,941 to Bailey et al., incorporated herein by reference, which employs a side impact or rollover protection restraint system comprising an air bag of sufficient length to extend from a vehicle A-pillar across a B-pillar and secured proximate a C-pillar. The system distributes inflation gas to the air bag through a flexible tube having a plurality of distributed openings along the length of the airbag. The airbag is bonded or sewn shut so that it will not be inflated in regions such as the back of the front seat or the B-pillar where injurious contact with a vehicle occupant is not expected. Although such a system reduces the amount of gas needed to inflate the bag and associated costs, the uninflatable region of the bag is nevertheless constructed of the same costly composites of fabric and thermoplastic as the inflatable region. Moreover, such air bags themselves must be custom designed to conform to a specific vehicle platform configuration, taking into consideration the number of side windows, side pillars, the presence of a third row of seating, etc.
Difficulties encountered in adjusting an airbag cushion system to differences between vehicle models become more pronounced when attempting to protect whole volumes of space in the event of a vehicle rollover, compared to, say, an airbag system deployed in front end collisions. Creating individualized airbags for every model of vehicle is expensive and might be cost prohibitive, especially for lower priced vehicle lines, not only in the design and manufacture of the airbag itself, but in installation costs as well. This would result in many vehicles not having sufficient airbag protection. Moreover, single airbag curtains can impede rescue efforts by hindering access to the vehicle interior, especially where the airbag maintains inflation after deployment.
Given the foregoing, it would be desirable to provide an airbag system that can protect a variety of internal vehicular surfaces, for a variety of different types of collisions, easy to manufacture and install, which minimizes the use of expensive composite containing fabric layer and weldable thermoplastic layer in areas which do not require cushioning during deployment of the airbag system. Moreover, it would be useful to provide a system that offers enhanced accessibility of the vehicle interior to rescue personnel after deployment.